The present invention relates to Doppler tracking methods, and more particularly, to Doppler tracking methods that provide for object imaging from radar returns.
Currently, the most widely known method of object tracking using an inverse synthetic array radar (ISAR) system is what is know as a "hot spot" tracker. The hot spot tracker relies on assumption that the object contains an isolated strong scatterer. Unfortunately, such a scatterer may not exist on any target and/or at any particular moment. The tracked scatterer often scintillates, which adversely affects image quality. The tracked scatterer may also fade away in terms of its radar cross section (RCS) or be blocked by other parts of the object as time goes on. If and when these events happen, another isolated strong scatterer must be acquired. Even if such a replacement scatterer is obtained, a transition period will exist during which images may jump and defocus in the Doppler dimension. These undesirable effects may be alleviated to some degree by using a long time constant for the tracking filter. However, the filter is less responsive to the dynamic motion of the object, such as acceleration or maneuvers, for example.
It is therefore an objective of the present invention to provide for a method for object imaging from radar returns while eliminating all of the above-cited difficulties.